I never understood Heraclitus' river analogy. Does it mean that we are constantly changing or changing only by degrees? Why does it say the "same" river if it is in constant flux? It seems like in the fragment "one can never step in the same river twice" that we could interpret the "step" as "never step in the same river" or as "never step into the same waters". Which is correct?

In Plato’s Cratylus, the character Socrates makes thefollowing comment about Heraclitus: “Heraclitus is supposed to say thatall things are in motion and nothing at rest; he compares them to thestream of a river, and says that you cannot go into the same rivertwice" (402a). Ever since Plato, the view that we can’t step twice intothe same river has been attributed to Heraclitus.

However,let’s consider the following two fragments about rivers that manyancient scholars regard as Heraclitus’ own words (in translation):

"On those who enter the same rivers, ever different waters flow– and souls are exhaled from the moist things" [B 12].

"We step and do not step into the same rivers, we are and we are not" [B 49a].

Inthe first fragment, Heraclitus suggests that we do step into the samerivers, even though the water in these rivers changes. The secondfragment raises interpretative problems of its own, but here tooHeraclitus speaks of the same rivers.

So how can we choosebetween the interpretation that Plato seems to give of Heraclitus, thateverything is always changing in every respect (a river is not even ariver from one moment to the next) and a less radical interpretationaccording to which Heraclitus is saying that things are always changingin at least some respect, but, for all that change, may well remainstable in at least some other respect?

Well, first it’s notclear that the position that Plato attributes to Heraclitus is evencoherent. But more importantly, it’s hard to reconcile Plato’sinterpretation with other Heraclitean fragments. Consider, for example:

"Theworld, the same for all, neither any god nor any man made; but it wasalways and is and will be, fire ever-living, kindling in measures andbeing extinguished in measures" [B 30].

Fire isclearly very volatile and is in a constant state of change, butnonetheless Heraclitus is suggesting here, it doesn’t change in respectof being fire. In fact, Heraclitus was reported by Theophrastus assuggesting that the change that an object undergoes in one respect canaccount for its stability in another respect:

"Things which have this movement by nature are preserved and staytogether because of it– if indeed, as Heraclitus says, the barley-drink separates if it is not moving" [B 125] (Theophrastus, On Vertigo 9).

Abarley drink cannot continue to be a barley drink over time, unlessit’s in constant movement. Fire can’t remain fire unless it’s inconstant movement. A river can’t remain a river, unless it’s watercontinues to flow. Or as Heraclitus says: